Mismatch of N release from the permafrost and vegetative uptake opens pathways of increasing nitrous oxide emissions in the high Arctic. (4th August 2022)

• Record Type: Journal Article
• Authors: Lacroix, Fabrice; Zaehle, Sönke; Caldararu, Silvia; Schaller, Jörg; Stimmler, Peter; Holl, David; Kutzbach, Lars; Göckede, Mathias
• Is Part Of: Global change biology. Volume 28:Number 20(2022)
• Page Start: 5973
• Page End: 5990
• Publication Date: 2022-08-04
• Subjects: carbon -- climate -- high Arctic -- nitrogen -- nitrous oxide -- permafrost -- vegetation; Climatic changes -- Environmental aspects -- Periodicals; Troposphere -- Environmental aspects -- Periodicals; Biodiversity conservation -- Periodicals; Eutrophication -- Periodicals; 551.5
• DOI: 10.1111/gcb.16345
• Languages: English
• ISSNs: 1354-1013

Abstract

Abstract: Biogeochemical cycling in permafrost‐affected ecosystems remains associated with large uncertainties, which could impact the Earth's greenhouse gas budget and future climate policies. In particular, increased nutrient availability following permafrost thaw could perturb the greenhouse gas exchange in these systems, an effect largely unexplored until now. Here, we enhance the terrestrial ecosystem model QUINCY (QUantifying Interactions between terrestrial Nutrient CYcles and the climate system), which simulates fully coupled carbon (C), nitrogen (N) and phosphorus (P) cycles in vegetation and soil, with processes relevant in high latitudes (e.g., soil freezing and snow dynamics). In combination with site‐level and satellite‐based observations, we use the model to investigate impacts of increased nutrient availability from permafrost thawing in comparison to other climate‐induced effects and CO2 fertilization over 1960 to 2018 across the high Arctic. Our simulations show that enhanced availability of nutrients following permafrost thaw account for less than 15% of the total Gross primary productivity increase over the time period, despite simulated N limitation over the high Arctic scale. As an explanation for this weak fertilization effect, observational and model data indicate a mismatch between the timing of peak vegetative growth (week 26–27 of the year, corresponding to the beginning of July) and peak thaw depth (week 32–35, mid‐to‐late August), resulting in incomplete plant use of nutrients near the permafrost table. The resulting increasing N availability approaching the permafrost table enhances N loss pathways, which leads to rising nitrous oxide (N2 O) emissions in our model. Site‐level emission trends of 2 mg N m −2 year −1 on average over the historical time period could therefore predict an emerging increasing source of N2 O emissions following future permafrost thaw in the high Arctic. Abstract : Our model and observation‐based approach shows an increase of deep‐soil nitrogen availability following permafrost thaw over the 1960 to 2018 time period. However, due to the disconnect of nitrogen release from thawed soil and uptake by vegetation, nitrogen loss pathways are opened, particularly leading to increased nitrous oxide emissions to the atmosphere. Thus, our results suggest that future thaw of the permafrost and associated increase in nitrogen release could cause an increasing disproportionate source of nitrous oxide to the atmosphere.